Find the wrong statement. - Vidyadip

MCQ

Find the wrong statement.

A
An electron gun is to create electrons and then accelerate them to a very high speed.
✓
Thermionic emissions and photoelectric emissions are the same.
C
The kinetic energy of photoelectrons vary.
D
Vacuum tubes are thermionic devices.

✓

Answer

Correct option: B.

Thermionic emissions and photoelectric emissions are the same.

No, thermionic emissions and photoelectric emissions are not the same. During thermionic emissions, the electrons are emitted from the metal surface by providing heat energy, whereas, during photoelectric emission light energy is emitted when electrons are emitted from the surface of the metal. So, it is the opposite in operation.

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